1. Field of the Invention
The present invention relates to a cooking vessel or utensil and, more particularly, to a wok for direct heating of food to prepare it. The cooking vessel of the present invention is provided with spherically or non-spherically curved surfaces and is designated as a wok because of its far-eastern origin. The present invention also relates to methods of making the cooking vessel.
2. Prior Art
Foods are preferably prepared in metallic or cast iron woks, which are heated from underneath by means of a gas flame or a wood fire, in a special manner in Asiatic regions. Meat, vegetables, rice are cooked together or separately first in the center of the wok, where it is at its hottest, and then pushed to the cooler edge. Everything is mixed prior to being served.
This typical wok cannot be used on a planar, especially electrically heated, cooking surface because of its spherical bottom. There are also xe2x80x9calteredxe2x80x9d woks made from cast iron, stainless steel or aluminum, which have a flattened bottom so that they can be used also on planar cooking surfaces. Since these altered woks also have an interior plane surface, the same cooking properties do not result, as in a typically spherical wok.
Also electrically heated table woks are known, in which a metallic dish is heated from below with a heated coil and is built into and fixed in a housing.
Woks are known from EP 0 629 820 A2, which are heated inductively. In these devices a cast ion, typically spherically formed wok, sits in a suitably formed porcelain or glass-ceramic dish, also designated a vessel, which for its part for example, is embedded in a working panel of a cooking range. Because of the residual heat in this heated metal wok, the porcelain dish may be thermally stressed too strongly, so that it can break or crack.
Furthermore all these commercially available woks with cast spherical or non-spherical metallic half shell vessels have the fundamental disadvantage that the materials to be finished frequently stick to it because of the large pore size on the interior surface of the wok, which frequently makes cleaning difficult. DE 298 20 731 U1 thus suggests providing the interior surface of the wok with a corrosion-resistant coating, which consists of hardened chromium with embedded PTFE. The application of this coating is very expensive.
It is an object of the present invention to provide a cooking vessel of the above-described kind, formed as a wokxe2x80x94cooking vessel for directly heating and preparing food, which is formed so that is universally heatable and requires no expensive interior coating.
According to the invention the wok or cooking vessel is made from hardened glass or glass-ceramic material with an appropriately small linear thermal expansion coefficient.
The method of making this sort of wok from hardened glass comprises the following steps:
a) preparing a pre-made hardened glass blank;
b) heating the hardened glass blank to its softening temperature immediately prior to the shaping or forming process;
c) shaping or forming the plasticized hardened glass blank to form the wok or cooking vessel, preferably by deep drawing, vacuum techniques or weight shaping techniques; and
d) cooling and tempering the wok or cooking vessel formed by the shaping or forming;
OR
a) preparing a piece of hardened glass;
b) shaping or forming the hardened glass piece by pressing, blowing or casting to make the wok or cooking vessel, and
c) cooling and temperature the wok or cooking vessel formed by the shaping or forming.
The method of making this sort of wok from glass-ceramics comprises the following steps:
a) preparing a moldable or formable, non-ceramic glass blank;
b) heating the hardened glass blank to its softening temperature immediately prior to the shaping or forming process;
c) shaping or forming the glass blank to form the wok or cooking vessel, preferably by deep drawing, vacuum techniques or weight shaping techniques;
d) ceramicizing the wok or cooking vessel after the shaping or forming; and
e) cooling the wok or cooking vessel after the ceramicizing.
The cover for the above-described cooking vessel, made according to the above-described methods, preferably is formed so that it is a curved or a substantially flat molded body made of hardened glass or glass-ceramic with a suitably small linear expansion coefficient.